Self-consistent field theory of polarized BEC: dispersion of collective excitation

TL;DR

This paper develops a quantum hydrodynamics framework for polarized Bose-Einstein condensates, deriving new equations to analyze how dipole interactions influence collective excitations and wave phenomena.

Contribution

It introduces a set of quantum hydrodynamics equations for polarized BECs, including polarization evolution and dispersion relations, extending the Gross-Pitaevskii equation to account for dipole-dipole interactions.

Findings

Derived dispersion relations for collective excitations in polarized BECs.

Identified a new type of collective excitation due to polarization dynamics.

Demonstrated wave generation mechanisms via polarized particle beams.

Abstract

We suggest the construction of a set of the quantum hydrodynamics equations for the Bose-Einstein condensate (BEC), where atoms have the electric dipole moment. The contribution of the dipole-dipole interactions (DDI) to the Euler equation is obtained. Quantum equations for the evolution of medium polarization are derived. Developing mathematical method allows to study effect of interactions on the evolution of polarization. The developing method can be applied to various physical systems in which dynamics is affected by the DDI. Derivation of Gross-Pitaevskii equation for polarized particles from the quantum hydrodynamics is described. We showed that the Gross-Pitaevskii equation appears at condition when all dipoles have the same direction which does not change in time. Comparison of the equation of the electric dipole evolution with the equation of the magnetization evolution is described. Dispersion of the collective excitations in the dipolar BEC, either affected or not affected by the uniform external electric field, is considered using our method. We show that the evolution of polarization in the BEC leads to the formation of a novel type of the collective excitations. Detailed description of the dispersion of collective excitations is presented. We also consider the process of wave generation in the polarized BEC by means of a monoenergetic beam of neutral polarized particles. We compute the possibilities of the generation of Bogoliubov and polarization modes by the dipole beam.